1. Field of the Invention
The invention relates to holographic spectroscopes, and, more particularly, to a holographic spectroscope which can be used with a two-motor reflection system such that the variety and the extensivity of the scanning patterns formed by the two-motor reflection system are improved.
2. Description of the Related Art
It is well-known that two-motor reflection systems are used in bar-code reading machines. U.S. Pat. No. 515,181 and European Patent No. 412,544 exemplify systems of this type. The two-motor reflection system includes two reflectors and two motors. Each reflector is connected to a motor which drives the reflector in the manner of a swash plate. Each motor is electrically connected to a control circuit operative to control the rotating speed of the motor. A light beam from a light source, such as a laser, is reflected first by one reflector and is then reflected by the other reflector. A scanning pattern formed by the two rotating reflectors is then projected onto a screen. The scanning pattern formed by the two-motor reflection system is similar to that of a lissajous curve or figure. If the rotating speed of the motor(s) is changed, or the angle of the reflector is changed, the scanning patterns also change. However, the variety of the scanning patterns effected by changes of the motor rotating speed or by changes in the angles of the reflectors is so limited that the varying scanning patterns differ from each other very little.
FIG. 1 is a schematic diagram of a conventional two-motor reflection system for projecting scanning patterns onto a screen. As shown, this two-motor reflection system includes a light source 10, such as an electric light bulb or a laser, for generating a light beam. A first rotatable reflector 11a is mounted in the optical path of the light beam from the light source 10 for reflecting that light beam. The first motor 12a rotatably drives the first reflector 11a in swash plate fashion and is electrically connected to a first control circuit 13a for controlling the rotating speed of the first motor 12a. A second reflector 11b is mounted in the optical path of the light beam from the first reflector 11a for reflecting that light beam onto a screen 16. The second motor 12b rotates a second reflector 11b and is electrically connected to a second control circuit 13b for controlling the rotating speed of the second motor 12b. In short, the two-motor reflection system includes principally the first reflector 11a, the first motor 12a, the second reflector 11b and the second motor 12b. It can generate different kinds of scanning patterns 15 by changing the rotating speed of the first motor 12a, or the second motor 12b, or by changing the angle of the first reflector 11a or the second reflector 11b. The scanning patterns 15 formed by the two-motor reflection system are then projected onto the screen 16.
The two-motor reflection system also can be used for entertainment at parties or in dance halls, alone or in combination with music or other rhythmic sounds. For example, the scanning patterns 15 formed by the two-motor reflection system may be changed by changing the rotating speed of the motor by or in synchronism with sound. If the sound is loud enough, for example, amplified music and clapping aloud, it can affect the rotating speed of the motor and make the scanning patterns 15 formed by the two-motor reflection system be more changeable and variable. However, a drawback of this system is that the changes of scanning patterns 15 formed by the two-motor reflection system tend to be largely repetition patterns. Another drawback to this two-motor reflection system is that the scanning patterns 15 are projected to a fixed location instead of to many different places and the extensivity of the scanning patterns 15 is poor. Therefore, the scanning patterns 15 are so similar and drab that they do not fulfill visual enjoyment by observers.